Shaking/rattling

Hey guys i keep noticing that my 07 classic 4.3 v6 keeps shaking if i keep it at 900(just over idleish) - 1600 RPM like when city driving im really conservative with the pedal and i mean theres not much slower that i can go without popping it into neutral and pushing it lol and i mean i already have one speeding ticket for going 58 in a 50 (kph) zone!! ****in cop in training it was such a joke like 26$ CDN! neways getting back to the point has anyone notcied this shaking/rattling? i brought it to the dealer when i got my first oil change at 2500kms and they said it just had to be broken in, its now almost got 8000 on it and it still does it especially tonight it was extra loud any help withthis would be appreciated!

I don't think there have been any design changes to the 4.3L engine in some time. The engine itself has a balance shaft to help smooth out the engine. I don't believe that balance shaft covers the entire rpm range, just the typical operating range. It's probably something you're going to have to live with. It's a possibility although unlikely, that the shaft has skipped a tooth, but then it would vibrate all the time.

ii didnt buy the truck or else it woulda been a crew with a 5.3 flex and active fuel management but neways my dad bought it withthe v6, a) because it was cheaper, b) because he wanted better fuel economy, but the v6 drinks it like nething, and not because the engine is no good or nething but that body imo is to heavy for a v6 to pull. Can you still get a 6 banger with the new gens? i think all trucks should be 8s

and as i was coming home i noticed a stain on my driveway, tried to smell it, but no odour im thinking its oil and gm did the stupid oil change! Im gonna try putting some water on it see if it repels it or if the water comes out different colors but man this truck is driving me nuts!

I'm actually surprised that GM is still offering the 4.3 in the full size truck. You're right it really is too heavy of a truck for that engine. They could get more efficiency out of a small v8 with 3.73 rear.
If they wanted an efficient 6 cyl they should drop the 4.2L TrailBlazer straight six into the full size truck.
The 4.3L V6 only has 195hp., where the 4.2L I6 has 291hp. At least with that extra power you could adjust your gearing appropriately for maximum economy.
I'm kind of confused why GM won't offer the I6 engine in the FS truck.